Nobody else knows why either... We don't know if the problem is in your microphone, amplifier circuit, or in your firmware/sketch, or somewhere else... In order to troubleshoot your project, you need to test the individual sections and "zoom-in" on the problem.

What's happening? Anything?

Do you have a multimeter to measure the signal out of your microphone amplifier? Maybe try putting +5V on the Arduino input to make sure the Arduino and the firmware are working. (With 5V, I assume the VU meter will max-out.)

Or, maybe add a protection circuit (two diodes and a resistor) and feed-in an audio signal from somewhere else (bypassing the microphone) .

Quote

I found a TDA2822M and the datasheet says its some kind of amplifier. Is it useful for this project?

Maybe... But it has fixed gain, and we don't know how much gain you need. The required gain depends on the sensitivity of the particular mic, and the loudness of the sound. Usually, it's best to have a gain/sensitivity control. And, you'd still need to bias the electret mic.

Nobody else knows why either... We don't know if the problem is in your microphone, amplifier circuit, or in your firmware/sketch, or somewhere else... In order to troubleshoot your project, you need to test the individual sections and "zoom-in" on the problem.

The last link in the first post leads to a description of what I already tried.

I assembled the circuit again. The arduino always reads a random value between 1000 and 1020.I connected 3 different microphones, one of them works with my PC. (I dindnt try the other ones) I tried both polarities for each microphone.Also, I connected the line out of my PC while playing music with the same result.The only way to get a signal, although a very weak one is to directly connect A0 to the PC and play music at maximum volume. Then it reads a tiny peak at each beat.

Do you have a multimeter to measure the signal out of your microphone amplifier? Maybe try putting +5V on the Arduino input to make sure the Arduino and the firmware are working. (With 5V, I assume the VU meter will max-out.)

The arduino works perfeclty with all my other projects.I hava a multimeter. (I actually bought it to debug this circuit when I tried it the first time)

Could be hardware failure, try to connect analog input directly to on board 3.3V and see what value you get.Applying AC voltage to any arduino pins, even it coming from your PC sound card , is something Never DO.